sendmail Performance Tuning

5.5. SMTP PIPELINING

Starting in version 8.12, sendmail implements support for SMTP PIPELINING. A complete description of this feature appears in RFC 2920 [FRE00]. A brief description will be given here. Basically, PIPELINING allows the sending of multiple SMTP commands without having to wait for a response from the server. Some commands can be sent in this manner, such as the transmission of SMTP envelope information. Some SMTP commands may not be pipelined, such as DATA, QUIT, and NOOP.

Let us consider a sample SMTP conversation without the use of PIPELINING. In the following examples, the client side of the conversation is prefaced with a “C:” and the server side of the conversation is prefaced with an “S:”. Lines preceded by neither an “ ...